The present invention relates to a copolymer of maleic anhydride and indene, an indene-based component having a reactive double bond, or other polymerizable components in naphtha oil. In particular, the present invention relates to efficient utilization of naphtha oil. The copolymer obtained by the present invention is useful as a resin modifier. The sulfonation product of the copolymer may be converted to a water-soluble salt form such as an alkali metal salt, an alkaline earth metal salt or an ammonium salt. These salts are useful as dispersants for dyes, pigments or ceramics, dispersants for coal-water slurries, stabilizers for drilling fluids or muds used in drilling geothermal, oil, or natural gas development wells, slump loss reducing plasticizer in cement mixes, textile aids, paper sizes, water treating agents, and as additives in printing inks.
The copolymer may also be esterified with alcohols and the resulting esterified product finds versatile use in such applications as paints, ink dispersants, adhesives, and leveling agents in floor polishing waxes.
Numerous techniques have been proposed regarding copolymers of maleic anhydride and monomers having reactive double bonds, as well as processes for producing them. Techniques for producing a styrene-maleic anhydride copolymer have been described in Japanese Patent Public Disclosure No. 60-206808, Japanese Patent Publication No. 48-43664, Japanese Patent Public Disclosure No. 62-197406, etc. These prior patents disclose a process for producing a styrene-maleic anhydride copolymer having a weight average molecular weight of not higher than 10,000, a method of regulating the molecular weight distribution of the copolymer by adding a dialkylaniline to the polymerization system for preparing the styrene-maleic anhydride copolymer, as well as an observation that describes the interrelationship between the rate of addition of a styrene-maleic anhydride monomer mixture to the reaction system, reaction temperature and the concentration of polymerization initiator. Japanese Patent Public Disclosure No. 62-3165 discloses the polymerization of an alkyl-styrene-styrene mixture and maleic anhydride.
Japanese Patent Public Disclosure No. 56-34006, Japanese Patent Public Disclosure No. 61-60084, Japanese Patent Public Disclosure No. 54-71136, etc. disclose a process for producing a copolymer of maleic anhydride and an alkene or diene having 4-6 carbon atoms such as butene, butadiene or isoprene. Thus, numerous techniques have become known regarding copolymers of maleic anhydride and hydrocarbons such as linear dienes or alkenes, or styrene or metylstyrene.
Makromol. Chem. 62, 120 (1963) describes copolymers of maleic anhydride and polymerizable components in naphtha oil but the yield of the resulting copolymer is as low as 76%. What is more, no mention is made of the composition of the naphtha oil used or the composition or molecular weight of the copolymer obtained.
Unlike styrene, indene which represents a major percentage of the polymerizable components (monomers having a reactive double bond) in naphtha oil is a bicyclic monomer containing a benzene ring to which is bound a cyclic side chain. The rate of formation of an indene-maleic anhydride copolymer is reported in J. Macromol. Sci., A Vol. 12, No. 8 (1978) but no review is made of an industrial process for producing such copolymer. U.S. Pat. Nos. 4,117,218 and 4,082,820 disclose processes for producing high-softening point resins from maleic anhydride and other monomers including indene and styrene. But these patents do not review the use of various dispersants produced by the disclosed processes.
Coal-derived naphtha oil which accompanies the dry distillation of coal, and petroleum-derived naphtha oil which is produced by thermal cracking of oils are both neutral oils having boiling points in the range of 80.degree.-220.degree. C. In these naphtha oils, indene-based aromatic hydrocarbon oils having reactive double bonds are contained in the form of a mixture, and no industrial process including separation and purification steps has been disclosed with respect to the production of copolymers from this mixture and maleic anhydride.
Japanese Patent Public Disclosure No. 60-206808 describes a process for producing a styrene-maleic anhydride copolymer using a ketone-based solvent. This process has the advantage of permitting consistent operations since the resulting copolymer will not adhere to the walls of the container or the agitating blades. Furthermore, this process allows the copolymer to be produced in high yield. However, because of the extremely high solubility of the copolymer in the solvent used, cumbersome procedures are necessary to separate and recover the copolymer, such as by charging the reaction solution into a poor solvent (i.e., a solvent in which the copolymer is slightly soluble) and recovering the copolymer as a precipitate.
Japanese Patent Publication No. 62-3165 describes a process in which a styrene containing a substituted alkyl-.alpha.-methylstyrene is reacted with maleic acid or derivatives thereof in the absence of a solvent to prepare a styrene-maleic acid copolymer. This method, however, is not suitable for industrial operations since the copolymer produced by solventless reaction adheres to the reaction vessel and agitating blades and is difficult to recover.
As described above, the thrust of the prior art is directed to the reactivity of copolymers in an attempt to produce them in high yield. No extensive reviews including efficient separation and recovery of copolymers have been made. Furthermore, copolymers of maleic anhydride and monomers having a reactive double bond are not simple in nature and the reactivity of monomers as well as the solubility of the resulting copolymers will vary depending upon whether the monomer is styrene, olefins having 3-8 carbon atoms or dienes. It is, hence, necessary to design an industrial production process that takes the characteristics of different monomers into account.
A copolymer of maleic anhydride and indene that have reactive double bonds are described in J. Macromol. Sci., A Vol. 12, No. 8 (1978) but the discussion is limited to the kinetics of reaction between indene and maleic anhydride and no review is made of an industrially advantageous process adapted for naphtha oil which contains in a mixture form indene and other polymerizable components having a reactive double bond.
Coke production from coal yields various useful components as by-products, among which is naphtha oil which is obtained as fractions over the boiling point range of 80.degree.-220.degree. C. No efforts have been made to develop new uses of this naphtha oil except for producing indene-coumarone resins in the presence of acid catalysts. The present inventors, therefore, conducted a study on the reaction between maleic anhydride and indene which represents a major percentage of the components in naphtha oil having a reactive double bond, or other components in naphtha oil having a reactive double bond or analogs thereof. As a result, it was found that the desired copolymers could be obtained in high yield from a homogeneous polymerization system but that in order to produce them on an industrial scale, the step of separating the resulting copolymer from the homogeneous solution was needed. A solventless polymerization system (bulk polymerization) has the advantage of obviating the need to separate the copolymer from a solvent but this approach also is not industrially advantageous since the copolymer produced adheres to the reaction vessel or agitating blades and is difficult to recover.
A styrene-maleic anhydride copolymer has recently attracted attention as a heat-resistant resin and it is known that the heat resistance of various resins such as ABS resins, polycarbonate resins (PC resins), polyvinyl chloride resins (PVC resins), polystyrene resins and nylons can be improved by incorporation of this copolymer. Detailed reviews have been made in Soc. Plast. Eng. Annu. Tech. Conf., vol. 45, No. 45, pp. 1384-1387 (1987) and J. Appl. Poly. Sci., vol. 32, No. 8, pp. 6131-6149 (1986). Plastics, vol. 35, No. 9, pp. 49-53 (1984) makes a similar review which states that a styrene-maleic anhydride copolymer starts to decompose thermally at a temperature around 200.degree. C., and that it is difficult to use this copolymer as a resin modifier.
As described above, the styrene-maleic anhydride copolymer starts to decompose thermally at a temperature around 200.degree. C., so it is not suitable for molding by extrusion or injection at temperatures exceeding 200.degree. C. because of various unwanted phenomena that would be encountered such as weight decrease due to the cleavage of the backbone chain of the copolymer or side chains, undesirable coloring and gasification of low-boiling point components. Thus, in spite of its superior performance that makes it potentially suitable for use as a resin modifier that is added to improve the resistance of general-purpose plastics or in the making of a heat-resistance improving resin composition, the styrene-maleic anhydride copolymer has not been used in practice.
Geothermal, oil and natural gas development wells are now commonly drilled by rotary drilling. In the rotary drilling method, a drilling fluid, usually called mud, is pumped down the drill pipe through nozzles in the drilling bit to remove formation cuttings from beneath the bit. The mud also reduces the heat of friction generated by the bit and prevents refracturing of the drill cuttings. As it circulates to the well head by ascending between the drill pipe and the walls of the hole, it transports the cuttings to the surface. In addition, the hydrostatic pressure of the mud column in the hole balances the formation pressure to prevent collapse of weak formations and influx of formation fluids into the well bore.
The mud which plays these important roles in rotary drilling is usually prepared by conditioning a suspension of water and clay with various additives. Clay is typically bentonite which is a montmorillonite-containing clay mineral or sepiolite which is a fibrous magnesium silicate. Commonly employed mud conditioners include sodium lignosulfonate, ferrochrome lignosulfonate, sodium humate, sodium salt of chrome humate and a lignin-humic acid complex. However, the mud prepared with these conventional conditioners does not have high heat resistance so that if it is used in drilling a hole in hot and high-pressure formations, it experiences increased dehydration and gels to form thick mud cakes on the walls of the hole, which might be a cause of drill pipe sticking to the hole. In addition, the recent environmental considerations require that muds containing large amounts of heavy metals be disposed of in an environmentally safe manner, and this substantially precludes the use of ferrochrome lignosulfonate and chrome humate which are comparatively more heat-resistant than other lignosulfonates and humates.
Japanese Patent Publication NO. 53-35875 proposes that a heat-resistant mud suitable for use in drilling a hole in hot formations be prepared by using a system in which alkali metal salts of humic acids are combined with a complex of natural fossil resin and natural asbestos. The mud prepared by this method is capable of withstanding a maximum of 180.degree. C. but at higher temperatures, it deteriorates gradually and becomes completely useless at 220.degree. C. Japanese Patent Publication No. 57-36306 proposes that the heat resistance of a drilling fluid composed of a clay mineral, an alkali salt of nitrohumic acids and water be improved by adding a coumarone-indene resin as a stabilizer. Even this mud is heat-stable up to a temperature of only about 220.degree. C.
Under these circumstances, U.S. Pat. Nos. 3,332,872 and 3,764,530 propose that alkali salts of a styrene-maleic anhydride copolymer or alkali salts of polyacrylic acid be used as mud stabilizers. Dispersants based on these polycarboxylates are more heat-resistant than lignosulfonates and humates but they suffer from the disadvantage that a marked increase in gel strength will occur as a result of prolonged use at about 220.degree. C.
In order for cement mixes (e.g. cement pastes, mortars and concretes) to have improved workability, they must exhibit high initial flowability and experience small change in flowability with time. The flowability of cement mixes in known to decrease with time due primarily to the reaction of hydration between cement and water and to physical aggregation of cement particles. Upon mixing the ingredients, hydration between cement and water occurs in cement mixes and as time lapses, physical and chemical aggregation of cement particles proceeds to reduce cement flowability and its workability and finishability will consequently decrease with time. This phenomenon is commonly referred to as "flow reduction" in mortars or "slump loss" in concretes and limits the "open time" of cement mixes. In the case of fresh concretes, slump loss causes various problems such as limited time of transportation, prolonged standby on the installation site and temporary interruptions of transfer by pumping, all these phenomena leading to undesirable effects such as deterioration of quality and low operational efficiency. Slump loss is also deleterious to fabricated concrete products since it limits molding time or causes insufficient centrifugal re-compaction. Therefore, slump loss, or time-dependent decrease in the flowability of cement mixes such as cement pastes, mortars and concretes, is a critical problem to be solved.
Several proposals have so far been made with a view to preventing slump loss in concretes. Japanese Patent Publication No. 51-15856 shows a method in which a concrete admixture selected either from water-soluble salts of sulfonated aromatic compounds or from water-soluble salts of the products of condensation between sulfonated aromatic compounds and formaldehyde is added repeatedly to concrete to maintain its flowability for a prolonged period. This method is effective to some extent but not only is it low in operational efficiency due to cumbersome procedures of addition of the admixture but it is also disadvantageous from an economic viewpoint.
Another method which involves the addition of a retarder such as an oxycarboxylic acid causes reduction in strength or insufficient hardening. Hydration of cement can be retarded by this method but it is very difficult to prevent physical aggregation of cement particles.
Japanese Patent Public Disclosure No. 54-139929 shows a method in which granules of a concrete admixture such as the product of condensation between naphthalenesulfonic acid and formaldehyde are added to concrete and dissolve slowly to prevent slump loss in the concrete. This method in effective to some extent in preventing slump loss but on the other hand, it is difficult to control the rate of dissolution of the admixture and residual admixture granules will reduce the strength and durability of the concrete.
Additives to be used to prevent slump loss in cements are also described in Japanese Patent Public Disclosure No. 59-141445 (the saponification product of a sulfonated styrene-maleic acid copolymer) and Japanese Patent Public Disclosure No. 60-11256 (the saponified product of a styrene-maleic acid copolymer). However, these additives, if used in small amounts, are not very effective in improving the flowability of cement mixes. Besides, they suffer from an economic disadvantage in that they have to be prepared from expensive materials.
As described above, none of the methods so far proposed for preventing slump loss are not completely satisfactory for practical applications. J. Petroleum Technology, p. 95 (1980) reports the use of a sulfonated styrene-maleic anhydride copolymer as a mud stabilizer but alkali salts of sulfonated styrene-maleic anhydride copolymer, if combined with several conditioners, are capable of providing muds that remain stable up to temperatures of about 250.degree. C. (U.S. Pat. No. 3,730,900). However, the need to drill deeper development wells for recovery of oils, geothermal energy and natural gas is expected to increase in the future and the problems to be encountered in deep-well boring will not be completely solved by the currently available mud stabilizers. It therefore remains desirable to develop a mud stabilizer of improved quality.
Copolymers of maleic anhydride and monomers having a reactive double bond, in particular, styrene or aliphatic hydrocarbon olefins having 4-6 carbon atoms may be used as such but more often than not they are put to use after at least part of the carboxylic acid groups is esterified by reaction with alcohols to impart desirable chemical or physical properties such as increase solubility in solvents and miscibility with other resins, although the polarity of carboxylic acid groups is left intact.
Esterification products of copolymers of maleic anhydride with monomers other than styrene have not been well characterized. The esterification of compounds having acid anhydrides generally proceeds until 50% of the carboxylic acid groups is esterified by the ring opening of acid anhydride groups if the compounds are heated together with alcohols with which they are to be esterified. However, the reaction rate is largely dependent on the molecular weight and structure of the compounds to be esterified and those of the lower molecular weight will undergo esterification with relative ease but difficulty is often encountered in esterifying compounds of the higher molecular weight. The reactivity of compounds is further reduced by the presence of large groups such as a benzene ring and a t-butyl group that adjoin the acid anhydride group to cause steric hindrance.
The conditions for esterifying a styrene-maleic anhydride copolymer or copolymers of maleic anhydride and olefins having 4-6 carbon atoms are known for individual cases and they differ from one resin formulation to another. Therefore, copolymers of maleic anhydride with styrene or olefins cannot be dealt with as one group and methods of their esterification must be considered individually.
Naphtha oil obtained from coal or petroleum contains components having reactive double bonds, a major proportion of which is represented by indene. Such indene or other components having reactive double bonds may be reacted with maleic anhydride to produce copolymers in an industrially feasible yield. In order to impart desirable physical and chemical properties to the copolymer while leaving the characteristic features of carboxylic acid groups intact, part of the carboxylic acid groups in the copolymer may be esterified by reaction with alcohols. The improved solubility of this copolymer in solvents or miscibility with other resins will help expand the scope in which it may be used. However, the method of esterifying maleic anhydride copolymers is largely dependent on the molecular weight or structure of the copolymer resin and specific conditions to be employed will differ from one resin to another. In particular, the esterification products of copolymers between maleic anhydride and indene or other components having reactive double bonds in naphtha oil derived from coal and the process for producing them have not been subjected to a serious review.